1. Field of the Invention
This invention relates to a method of font generation, and more particularly to a method of font generation for displaying the thickness of strokes of a character.
2. Description of the Prior Art
In general, fonts produced by descriptive methods of characters comprise three types: a bitmap font, an outline font, and a vector font. The three types of descriptive methods of characters are described below.
(1) Bitmap Font:
A descriptive method of a bitmap font is displayed in pixels. As shown in FIG. 1A, an area 2 shown in oblique lines is displayed in an area of the font and a white area 4 without oblique lines is displayed in an outer area of the font. Therefore, the bitmap font is an image of a font and displays the form of a font accurately in a fixed size of the font. Furthermore, the bitmap font easily displays characters in a monitor. However, a disadvantage is that data of the font are large. Moreover, due to the fact that the bitmap font is an image and the size of the bitmap font is fixed, a resized font has a problem with distortion. Hence, the bitmap font is not fit for resizing and a resized font is not a refined and beautiful one.
(2) Outline Font:
As shown in FIG. 2A and FIG. 2B, an outline font is described by means of curves and strokes controlled by control points 8. An outline 10 of an outline font is described by curves. An area surrounded by the curves is a form of the font, as shown in FIG. 1B. In general, a bend of the outline 10 thereof is displayed in a quadratic curve (second-order function) or a cubic Bézier curve (third-order function). Furthermore, the curves of the outline font are described by the stroke thickness of the font. Because of the bend of the outline 10 and the thickness of strokes, the font can be described exquisitely with starting and ending control points 6 and control points 8. The outline font is thereby refined and looks beautiful. Moreover, when compared with a bitmap font, an outline font has less data. A resized outline font still looks refined and beautiful as its original outline font. Therefore, the outline font, e.g., TrueType Font or PostScript, becomes a popular font. A set of Chinese, Japanese, or Korean (CJK) fonts generally includes approximately 7,000 to 18,000 characters in about 5 to 12 mega bytes. For a PDA (“personal digital assistant”), set-top box or cellular phone, the amount of characters stored in these apparatuses is limited due to limitation of memory space.
(3) Vector Font:
A vector font is described by means of central curves and strokes controlled by control points 8, as shown in FIG. 1C. Due to the lack of form description and thickness of strokes, the vector font limits a font 12 to be a lightface or boldface. Therefore, an appearance of font 12 is not refined or beautiful as that of an outline font. However, data of a vector font include mainly central curves of strokes without variants of the form of characters. Hence, the amount of data thereof can be efficiently reduced. As compared with a bitmap font or an outline font, the amount of data for a vector font is minimum. Moreover, a resized font can be performed without distortion.
A current trend of development in information appliances is mobile and exquisite. However, memory limitation in a device will result in a serious problem. Hence, it is desired to have a new descriptive method of characters which not only saves more characters under the limitation of memory and low-resolution of display screens, but also transmits the characters through a limited bandwidth in a shorter time. The present invention can overcome the aforementioned disadvantages and describe refined characters and economize memory.